Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of the common general knowledge in the field.
Ice cream is a frozen dessert made from ingredients such as cream, milk and eggs and often combined with fruits or other ingredients and flavours. Cream or butterfat gives ice cream its creamy flavour and texture. Milk gives it body and makes it smooth. Stabilizers, such as eggs or gum, are added to give the frozen blend a smooth texture by preventing large ice crystals from forming during the freezing process. Sugar and other flavourings provide sweetness and add to the taste of ice cream. Natural flavourings, such as chopped or whole fruits or nuts, also add a variety of different textures.
The basic liquid ingredients are mixed inside a bowl until it reaches a smooth and consistent consistency before the ice cream is made. Some recipes require this mixture to be heated to produce a smoother, better tasting ice cream. Commercially ice cream production also introduces a pasteurisation process where this mixture is heated to a specific temperature for a length of time, and then cooled immediately. This process slows the growth of bacteria and is required for the commercial production of ice cream.
The most common method for producing ice cream at home is to use an ice cream maker. In modern times this is generally an electrical device that mixes the ice cream mixture while it is cooled inside a household freezer, or using a solution of pre-frozen salt and water, which gradually melts while the ice cream freezes. A domestic ice cream maker is used to make small quantities of ice cream at home. Ice cream makers may stir the mixture by hand-cranking or with an electric motor, and may chill the ice cream by using a freezing mixture, by pre-cooling the machine that requires the ice cream bucket being pre-frozen in a conventional freezer, or by the machine itself using a compressor (similar to a refrigerator).
An ice cream maker must freeze the mixture, and must simultaneously stir or mix it to prevent the formation of ice crystals and to produce smooth and creamy ice cream. The stirring process may also be used to whip or entrain air into the mixture to make the final product light and fluffy.
There are a number of different types of ice cream makers available on the market, but for the purposes of the teachings in this document, we will concentrate on the electrically operated machines. These commonly use an electric motor to drive a blade that in turn mixes the ice cream, whilst cooling is achieved by one of 3 methods.
In one method a double walled bowl is used that contains a solution that freezes below the freezing point of water. This is frozen in a domestic freezer for up to 24 hours before the machine is needed. Once frozen, the bowl is put into the machine, the mixture is added and the machine is switched on. The paddles rotate, stirring the mixture as it gradually freezes through contact with the frozen bowl. Twenty to thirty minutes later, the solution between the double walls of the bowl has thawed, and the ice cream has frozen.
In a second method, the bowl and its contents are mixed inside a domestic freezer. These devices can either be battery powered or the type when the freezer door closes over a power cord which is plugged into a power point outside of the freezer.
In a third method machines have a compressor type freezing mechanism built in and do not require the bowl to be pre-chilled. The cooling system is switched on, and in a few minutes the mixture can be poured in and the motorised blade switched on.
In this document the term ice cream mixture refers to the precursor ingredients in or contents of an ice cream making machine at a time prior to completion of a batch of finished ice cream.
Ice cream making machines are well known. Some utilise salted ice and other machines rely on a compressor for refrigeration. Popular styles of ice cream require the user to add flavouring and texture ingredients referred to as “mix-ins” at some time after the ice cream making process has begun. Further, although users prefer ice creams of different hardnesses, most machines deliver a finished ice cream of a single hardness, given a particular pre-mixture of ingredients.
The international distribution of such machines sometimes requires the fitting of either a 120 or 220-240 volt motor, depending upon the ultimate destination of use of the machine. Different motors have different torque characteristics. When a machine depends on a direct or indirect measurement of motor load or torque or ice cream hardness, achieving the same torque with different motors can be problematic.